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[NamePlate]

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[BGuttman]

I don't think you can find a King single valve bass. The 5B is basically a large tenor and the other basses, 6B, 7B, and 8B are all double valve.

Make sure they know the difference between a tenor with F-attachment and a true bass. Adding a Gb to a tenor won't make it a bass. Just a tenor with two valves. Also,it won't fit your oversize bell.

I'll leave it to the Techs to price out a Gb section and a bell transplant.

[Burgerbob]

Single basses will have a full size everything, but only one valve. Sounds as though they found F attachment tenor trombones if they have 8.5 inch bells. I definitely wouldn't spend any money making a tenor into a bass.

[NamePlate]

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[hyperbolica]

You're gonna spend WAY more time and money trying to turn a pile of junk into a double valve bass than you will by just buying a used or even chinese double valve bass. Unless you can do your own work, the method you describe turns out to be the most expensive way to get where you're going. It's a better idea to just buy a used instrument for under $2000. You'll be way ahead of the game.

[NamePlate]

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[Burgerbob]

Even by your own estimates, you're looking at $1700. I'd save up a bit of money and buy a used double for around that much and save a lot of time and hassle.

[Posaunus]

... could not find a double rotor bass trombone in there but found a few single rotor basses. ... I have a few questions about the viability of modifying it into a true bass.

2) I would like to increase the bell size ... from 8.5" to 9.5"

• A single-rotor bass trombone (e.g., Yamaha) is a "true bass" trombone - same bore size and same bell size bell as most double-rotor bass trombones. It just has one valve instead of two. If you're still in high school, playing typical repertoire, you may not find much use for that second valve.

• A single rotor trombone with an 8.5" diameter bell is a large tenor trombone (probably 0.547" bore), not a bass trombone (0.562" or 0.563" bore).